Shelf unit



FIG. 1 is a front and left side perspective view of a shelf unit showing my new design;

FIG. 2 is a rear elevational view;

FIG. 3 is a top plan view;

FIG. 4 is a right side elevational view;

FIG. 5 is a front elevational view; and

FIG. 6 is a bottom plan view thereof.

FIGS. 2-6 have been shown on an enlarged scale with respect to FIG. 1. 

The ornamental design for a shelf unit, as shown and described. 